Methods and apparatus for selection of dedicated core network

ABSTRACT

Methods and apparatuses for redirecting a wireless transmit/receive unit (WTRU) to a dedicated core network (CN) node are described. An apparatus is configured to initiate a Service Request with a non-dedicated network node. The apparatus is configured to receive a special identifier in response to the Service Request, which indicates the apparatus should be redirected to a dedicated CN node based on subscription information. Radio access network resources associated with the apparatus may be released and the apparatus may then perform a tracking area update (TAU) request which is then forwarded to the dedicated CN node.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/002,246, filed Aug. 25, 2020, which issued as U.S. Pat. No.11,228,956 on Jan. 18, 2022, which is a continuation of U.S. patentapplication Ser. No. 16/385,529, filed Apr. 16, 2019, which issued asU.S. Pat. No. 10,757,626 on Aug. 25, 2020, which is a continuation ofU.S. patent application Ser. No. 15/959,701, filed Apr. 23, 2018, whichissued as U.S. Pat. No. 10,264,498 on Apr. 16, 2019, which is acontinuation of U.S. patent application Ser. No. 15/309,574, filed Nov.8, 2016, which issued as U.S. Pat. No. 9,955,393 on Apr. 24, 2018, whichis the U.S. National Stage, under 35 U.S.C. § 371, of InternationalApplication No. PCT/US2015/029999, filed May 8, 2015, which claims thebenefit of U.S. Provisional Application No. 61/990,543, filed May 8,2014, U.S. Provisional Application No. 62/014,356, filed Jun. 19, 2014,and U.S. Provisional Application 62/017,628, filed Jun. 26, 2014, thecontents of which are hereby incorporated by reference herein.

BACKGROUND

A wireless transmit/receive unit (WTRU) may run a variety of servicesand applications over cellular networks that are defined in The 3rdGeneration Partnership Project (3GPP). An example of a service definedby 3GPP is voice. Some WTRUs, for example smart phones, are operated byhumans and the WTRUs then execute 3GPP procedures. Examples of 3GPPprocedures may include requesting an Internet protocol (IP) address orresources with a specific quality of service (QoS). However, other WTRUsmay not necessarily interact with humans but may run applications thatvary from smart meters to sensors, among others, and may be referred toas machine type devices which may communication via machine typecommunication (MTC).

Cellular operators are expected to operate their networks with anever-increasing number of machine type devices, which may cause serviceissues as a result, such as increased load on the cellular system.Accordingly, cellular operators may prefer to deploy dedicated nodesthat may only serve devices that match one or more specificcharacteristics, such as devices that are known to be machine type, thathave a very predictable communication pattern, or whose IP connection isrequired to meet a specific communication model or treatment. Byemploying dedicated nodes, the cellular operator may ensure that WTRUsthat are used by humans always get the expected QoS.

Cellular operators are expected to operate their networks with anever-increasing number of M2M devices, which may cause service issues,such as increased load on the cellular system, as a result. Accordingly,cellular operators may prefer to deploy dedicated nodes that may onlyserve devices that have a specific characteristic. Examples of deviceshaving a specific characteristic include devices that are known to bemachine type, that have a very predictable communication pattern, orwhose IP connection is required to meet a specific communication modelor treatment. By employing dedicated nodes, the cellular operator mayensure that WTRUs that are used by humans, such as smart phones, alwaysget the expected QoS.

SUMMARY

Disclosed is a method and apparatus configured to execute the method.The method may be for redirecting a wireless transmit receive unit(WTRU) to a dedicated core network (CN) node. An embodiment of themethod may include determining, based on subscription information, thatthe WTRU should be redirected to the dedicated CN node. An embodiment ofthe method may further include receiving, from the WTRU, a servicerequest, such as a service request for an Internet Protocol (IP)connection. An embodiment of the method may further include in responseto the service request, allocating a global unique temporary identity(GUTI). An embodiment of the method may further include transmitting, tothe WTRU, the GUTI in response to the service request.

In an embodiment of the method, the GUTI may include a null MME groupidentifier (null-MMEGI), wherein a value of the null-MMEGI may indicatethe dedicated CN node.

An embodiment of the method may further include receiving, from theWTRU, a tracking area update (TAU) request. An embodiment of the methodmay further include redirecting the WTRU to the dedicated CN node basedon the null-MMEGI in response to the TAU request.

In an embodiment of the method, the redirecting may include forwardingthe TAU to the dedicated CN node.

An embodiment of the method may further include, in response to thedetermining, paging the WTRU to bring the WTRU into connected mode.

An embodiment of the method may further include receiving thesubscription information from a home subscriber server (HSS), whereinthe subscription information may be pushed subscription information.

In an embodiment of the method, the receiving the pushed subscriptioninformation may trigger the MME to execute the determining.

In an embodiment of the method, the pushed subscription information mayindicate a change in the subscription information, and the pushedsubscription information may indicate that the WTRU should be servicedby the dedicated CN node.

An embodiment of the method may further include paging the WTRU inresponse to the change in the subscription information.

In an embodiment of the method, the pushed subscription information mayinclude a CN node type parameter that indicates a dedicated CN nodetype.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a diagram of an example method of WTRU redirection to adedicated core network (CN) node at attach;

FIG. 3 is a diagram of an example method of WTRU redirection to adedicated CN node after authentication information request/response;

FIG. 4 is a diagram of an example method of WTRU redirection to adedicated CN node using a specific global unique temporary identity(GUTI) and a non-broadcast tracking area identity (TAI);

FIG. 5 is a diagram of an example method of WTRU redirection to adedicated CN node using a null mobility management entity groupidentifier (MMEGI);

FIG. 6 is a diagram of an example method of WTRU redirection to adedicated CN node using MME-triggered S1 handover;

FIG. 7 is a signaling diagram of an example method of a WTRU beingredirected to a dedicated CN node when a WTRU sends a Service Request;

FIG. 8 is a diagram of an example method for a WTRU to switch from adedicated CN node to a non-dedicated CN node;

FIG. 9 is a diagram of an example method for a dedicated CN node toinitiate a WTRU to switch back to the non-dedicated CN node;

FIGS. 10A and 10B are a diagram of an example method for performing WTRUredirection;

FIG. 11 is a diagram of an example location update procedure initiatedby the MME; and

FIG. 12 is a diagram of an example international mobile subscriberidentity (IMSI) detach procedure when a dedicated MME does not supportCSFB functionality.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a site controller, an access point (AP),a wireless router, and the like. While the base stations 114 a, 114 bare each depicted as a single element, it will be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple-output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 10 is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNode-Bs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 140 a, 140 b, 140c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 140 a, 140 b, 140 c may implement MIMO technology. Thus,the eNode-B 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 10 , theeNode-Bs 140 a, 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 10 may include a mobility managemententity gateway (MME) 142, a serving gateway 144, and a packet datanetwork (PDN) gateway 146. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MME 142 may be connected to each of the eNode-Bs 140 a, 140 b, 140 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 144 may be connected to each of the eNode Bs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

In order for a cellular network operator to service WTRUs that have acertain characteristic with a dedicated CN node, such WTRUs may need tobe redirected to the dedicated CN node. A dedicated CN node may includean MME, serving gateway (SGW), or packet data network gateway (PGW).This redirection of WTRUs may be done based on subscription information,which may be stored at a home subscriber server (HSS). The MME maydownload the subscription information when the WTRU registers orattaches to the network.

A WTRU that is running a machine type application or is otherwise of lowpriority may normally indicate that it is a low access priority device(LAPD) using an LAPD indication, which the WTRU may signal when it firstaccesses the network. The WTRU may signal its low access priority statusat the radio (i.e., radio resource control (RRC)) and non-access stratum(NAS) levels. The network may use this indication to take certainmeasures if needed, for example to apply congestion control by providingsuch devices with back-off indications and timers. However, for an LAPDthat is to be redirected to a dedicated CN node, the system information(SI) may not make use of WTRU indications but may rely on subscriptioninformation. The subscription information may contain an indication thatthe device in question should be served by a dedicated CN node. Sincethe subscription information may change at any time, the time at which aWTRU may be redirected toward a specific CN node may not be defined.Redirection may take place, for example, when any of the followingprocedures occur: attach, tracking area update (TAU), routing areaupdate (RAU), Service Request, intra-RAT idle mode mobility, inter-RATidle mode mobility, intra-RAT handover, inter-RAT handover, roaming or asharing network scenario. A Service Request may, for example, request anIP connection. The IP connection may establish a data connection tocommunicate data to and/or from the WTRU.

Example methods of WTRU redirection to a dedicated CN node are describedbelow with respect to FIGS. 2, 3, 4, 5 and 6 .

FIG. 2 is a diagram of an example embodiment of a method of WTRUredirection to a dedicated CN node at attach. In the embodiment shown inFIG. 2 , the WTRU 210 may transmit an Attach Request 201 to an eNB 220which may then forward the Attach Request 201 to an MME 230. The AttachRequest 201 may include an IMSI. The MME 230 may contact an HSS 250 andexchange Update-Location-Request/Answer (ULR/ULA) commands 202 with theHSS. The MME may retrieve the WTRU subscription profile 202 from the HSS250. The subscription profile may include an indication that the WTRUshould be redirected to a dedicated CN node. The HSS 250 may inform theMME 230 that the WTRU 210 may select a CN node type in the subscriptiondata.

The MME 230 may then send an S1AP reroute command message 203 to the eNB220 in which the CN node type parameter and global unique temporaryidentity (GUTI) may be provided. The IMSI-based attach may be convertedto a GUTI-based Attach Request 204. The eNB 220 may select a dedicatedMME 240 based on the CN node type and send the GUTI-based Attach Request204 to the dedicated MME 240. The dedicated MME 240 may contact thefirst MME 230, retrieve the security parameters 205 and then continuewith the attach procedure. It is possible for the dedicated MME 240 tocommunicate with the WTRU 210 by using the first MME's security key. Thededicated MME 240 may also select a new SGW or PGW 260 and establishbearers 206. The dedicated MME 240 may also contact the HSS 250 toperform ULR/ULA commands 207 to update the location information of theWTRU 210 in the HSS 250.

Although the example method depicted in FIG. 2 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 3 is a diagram of another example method of WTRU redirection to adedicated CN node. In the example illustrated in FIG. 3 , the WTRU 310may send an Attach Request 301 to the eNB 320. The eNB 320 may thenforward the Attach Request 302 to an MME 330. The MME 330 may thenexchange Identity Request/Response messages 303 a and 303 b, for examplewith the old MME/SGSN 340 or the WTRU 310, to obtain the IMSI. The WTRU310, MME 330, and HSS 360 may exchange Authentication Informationmessages 305 including an Authentication Information Request 305 a andAuthentication Information Response 305 b. The MME 330 may receive theCN type parameter from the HSS 360 when receiving the AuthenticationInformation Response message 305 b. The MME 330 may then send a reroutecommand message 306 to the eNB 320, which may include the Attach RequestMessage and the Core Network Type parameter indicating a dedicated CNtype. The eNB 320 may then send an Attach Request message 307 to adedicated MME 350.

Although the example method depicted in FIG. 3 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 4 is a diagram of an example method of WTRU redirection to adedicated CN node using a specific GUTI, which may be allocated by anMME, and a non-broadcast tracking area identity (TAI). The GUTI may bemade up of identities in accordance with the following:GUTI=<PLMN ID><MME Group ID><MME Code><M-TMSI>,where PLMN is an abbreviation for Public Land Mobile Network, and M-TMSIis an abbreviation for a unique Temporary Mobile Subscriber Identity(TMSI) within the MME that allocated the GUTI.

The M-TMSI is a unique 4 octet value that may identify the WTRU withinthe MME and the MME Code (1 octet) represents the specific MME withinthe identified MME Group ID (2 octets). The Globally Unique MMEIdentifier (GUMMED, may be made up of identities in accordance with thefollowing:GUMMEI=<PLMN ID><MME Group ID><MME Code>.

Hence, the GUTI may also be expressed as:GUTI=<GUMMEI><M-TMSI>.

In the example illustrated in FIG. 4 , the WTRU 410 may transmit anAttach Request 401 to the eNB 420 which may then forward the AttachRequest 401 to an MME 430. The MME 430 may contact an HSS 460 andexchange Update-Location-Request/Answer (ULR/ULA) commands with the HSS460. The MME 430 may retrieve the WTRU subscription data 402 from theHSS 460. The subscription data 402 may include an indication that theWTRU 410 should be redirected to a dedicated CN node. The HSS 460 mayinform the MME 430 that the WTRU 410 may select a CN type parameter inthe subscription data. The MME may establish bearers 403 forcommunicating with the SGW 450.

The MME 430 may allocate a specific GUTI, which may include the mobilitymanagement entity group identifier (MMEGI) of the dedicated MME 440 andsend it to the WTRU 410, for example through the eNB 420, in an AttachAccept message 404. The WTRU 410 may then eventually send a TAU Request405 with the MMEGI of the dedicated MME 440. The MME 430 may also send anon-broadcast TAI, for example 0000 or FFFF, to cause the WTRU 410 toperform the TAU request 405. The MME 430 may also have a MMEGI. TheMMEGI of the MME 430 and the dedicated MME 440 may be pre-configured.The eNB 420 may route the TAU Request 405 to the dedicated MME 440 basedon the MMEGI. The dedicated MME 440 may then perform an identificationprocedure 406 with the MME 430 to get context information from the MME430. The dedicated MME 440 may establish bearers 407 for communicatingwith the dedicated S/PGW 470. The dedicated MME 440 may also contact theHSS 460 to perform ULR/ULA commands 408 to update the locationinformation of the WTRU 410 in the HSS 460.

Although the example method depicted in FIG. 4 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 5 is a diagram of an example method of WTRU redirection to adedicated CN node using a null-MMEGI. The example illustrated in FIG. 5is similar to the example illustrated in FIG. 4 except that, in thisexample, the MME 530 may allocate a specific GUTI that includes anull-MMEGI of the network that the dedicated MME 540 belongs to plus theMME code (MMEC) of the MME 530. When the WTRU 510 performs a TAU Request505, the eNB 520 may route the TAU Request 505 to the dedicated MME 540according to the null-MMEGI. The dedicated MME 540 may then contact theMME 530 since the MMEC was contained in the GUTI and may start thecontext request/response procedure 506.

Although the example method depicted in FIG. 5 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 6 is a diagram of an example method of WTRU redirection to adedicated CN node using MME-triggered S1 handover. In the exampleillustrated in FIG. 6 , an attach procedure 601 is performed. In thisexample, the MME 630 may establish a packet data network (PDN)connection with the dedicated S/PGW 650 based on PDN connectioninformation in the subscription information provided by the HSS 640.Once the attach procedure 601 is completed, the MME 630 may trigger ahandover 602 toward the dedicated MME 660 using a new message on the S1interface. However, the serving cell and eNB 620 may not change as apart of the handover. The MME 630 may send a Forward Relocation Request604 to the dedicated MME 660. The dedicated MME 660 and the eNB 620 maythen exchange Handover Request/Acknowledge messages 605. The dedicatedMME 660 may then send a Forward Relocation Response 606 to the MME 630.The MME 630 may then send a Handover Command 607 to the eNB 620. Thededicated MME 660 may then exchange Update Location Request/Responsemessages 608 with the HSS 640.

Though not depicted in FIG. 6 , measurements, data forwarding, statustransfers, SGW relocation, and handover notification steps may beincluded in the example method of FIG. 6 . Furthermore, although theexample method depicted in FIG. 6 shows messages and/or steps in aparticular order, it should be recognized that not all messages and/orsteps may be necessary and the particular order may be different.Furthermore, whereas steps and/or messages may be depicted as separateevents, the steps and/or messages may be combined as a single event.Likewise, a single event may be broken out into multiple events.

Additional procedures may be implemented to augment the examplesdescribed above with respect to FIGS. 2, 3, 4, 5 and 6 . For example, amechanism may be implemented which routes a security context from oneMME to another, where the source MME may initiate the routing. A targetMME may request WTRU context/security parameters from a source MME.Additionally, a WTRU may request a dedicated bearer activation before anattach procedure completes. The system may need to execute thisprocedure such that it is forwarded or finally executed by the dedicatedMME.

For embodiments that include the WTRU performing a TAU in order for theeNB to select a dedicated CN node, a WTRU may remain served by asub-optimal CN node for a long time because it may take a long time toexecute this procedure.

In addition, some WTRUs may perform combined registration to thepacket-switched (PS) and circuit-switched (CS) domains via an MME, whichmay register the WTRU for the PS domain and then contact the mobileswitching center (MSC)/visitor location register (VLR) to register theWTRU in the CS domain. While the MME may be a dedicated MME for thisdevice, the MSC/VLR may not be, and, therefore, a better choice for theMSC/VLR may be made. Mechanisms may be needed to address this scenario.

Also, a WTRU may be switched back from a dedicated CN node to anon-dedicated CN node for a number of different reasons. For example,the dedicated CN node may be overloaded or malfunctioning due tohardware or software failure, or the WTRU may be scheduled to stay witha dedicated CN node for a configured period of time. A mechanism mayswitch the WTRU from the dedicated CN node to a non-dedicated CN node.

Further, since diverse classes of devices may have different trafficcharacteristics and data usage requirements, separate dedicated CN nodesmay be needed to efficiently support these classes. However, a devicemay not necessarily be limited to a single type of traffic or datausage. The device may support various types of activities and behaviorsover its lifetime. For example, a device may be configured to runmachine type applications, for example reporting automated measurements,at one point in time, while at another point in time the same device maybe used with human interaction for a different type ofservice/application. In this case, the device may be redirected from onededicated CN node to another in order to meet the communicationrequirements/characteristics of the specific service the device iscurrently using. Thus, a mechanism to support the relocation of a WTRUfrom one dedicated CN node to another may be needed.

In addition, a WTRU may be redirected to a dedicated CN node after anattach/TAU/RAU procedure using a CN triggered handover that may changethe MME to which the eNB connects. This procedure may be transparent tothe WTRU. However, during the attach/TAU/RAU, a first, serving MME mayhave allocated a GUTI that maps to the first, serving MME itself. Thus,if a CN-triggered handover is performed, the GUTI of a WTRU may be thesame GUTI provided by the first, serving MME. The implications of thismay be that when the WTRU later enters an idle mode, for example afterits CN node has been redirected, it may send a Service Request messageto transition to a connected mode. As part of the Service Requestprocedure, the WTRU may use its SAE temporary mobile subscriber identity(S-TMSI) in the RRC connection establishment procedure, for example inthe RRC connection request message that is sent to the eNB,wherein S-TMSI=<MMEC><M-TMSI>.The S-TMSI may identify the specific MME that has the WTRU context.Thus, if, after the CN-triggered handover, the GUTI is not re-allocated,the identities of a WTRU may point to the old MME, which may havedeleted the context of the WTRU since a dedicated CN has already beenselected per the CN-triggered handover.

Additionally, a WTRU that is already registered or attached to thesystem may be allocated a GUTI, part of which may be the S-TMSI. Duringan RRC establishment procedure for sending a NAS message, for example aTAU or Service Request, the WTRU may include the S-TMSI in theRRCConnectionRequest message. The GUMMEI may be included in theRRCConnectionSetupComplete message. After the eNB receives theRRCConnectionSetupComplete message, the eNB may have both the S-TMSI andthe GUMMEI. The GUMMEI may point to the registered PLMN and the MMEgroup, while the S-TMSI may contain the MME code that points to thespecific MME within the MME group as identified by the MMEGI.

In the case of null-MMEGI, the eNB may receive a null-MMEGI that pointsto a dedicated MME and an S-TMSI that points to the non-dedicated MMEthat currently has the WTRU context, for instance the MME that allocatedthe GUTI with the null-MMEGI. Thus, the NAS message, for example the TAUor Service Request, may be forwarded to the dedicated MME based on thenull-MMEGI. If the NAS message is a TAU, the TAU may force the dedicatedMME to fetch the WTRU's context from the non-dedicated MME. However, ifthe NAS message is a Service Request and this NAS message is sent to thededicated MME, the dedicated MME may not be able to fetch the WTRU'scontext. Therefore, the MME may reject the WTRU possibly with a causecode “#9—WTRU identity cannot be derived by the network” that may causethe WTRU to re-attach to the system and also delete its allocated GUTIwhich points to the dedicated CN. In this scenario, the process may berestarted again.

The use of a dedicated CN node may take several forms. For example, adedicated CN may include the use of a dedicated MME, a dedicated SGW,and a shared PGW. In another network, the policy to use a dedicated CNmay also include the use of dedicated PGW. If a WTRU is alreadyregistered or attached to the system, its PGW may already be selected.Generally, PGW selection may occur during the attach procedure. Thus, ifa WTRU is required to use a dedicated PGW, the WTRU may perform PGWselection again. As a result, the WTRU may perform a re-attachprocedure. It may also be possible for the WTRU to reselect a PGWwithout the WTRU performing a re-attach. If the WTRU performs are-attach, this re-attach may be done at the serving MME or may be doneat the dedicated MME. Both options may have certain advantages anddisadvantages. For example, if the re-attach is performed at the servingMME, which may be a non-dedicated MME, the serving MME may incur thissignaling. After the attach procedure is completed the serving MME mayattempt to redirect the WTRU to a dedicated MME. Moreover, anappropriate PGW may have been selected by the previous serving MME.Since the purpose of the redirection may be to relieve the non-dedicatedMME from this WTRU, this embodiment may force some signaling on thenon-dedicated MME. Thus, different methods may be used for re-attachingthe WTRU at either the source non-dedicated MME or at the targetdedicated MME after redirection.

If a WTRU is registered both in an MME and an MSC/VLR for the use ofcircuit switched fallback (CSFB), an MME initiated S1 handover, asdescribed above, may relocate the WTRU to a dedicated MME. However, theWTRU may not be able to use CSFB because the dedicated MME may not havethe CSFB context and the VLR may maintain the SGW associated with theold MME. Thus, a method to establish an SGW association between the newdedicated MME and the MSC/VLR is desired.

Embodiments are described herein that may provide procedures andmechanisms to enable redirection of a WTRU to a dedicated CN node, forexample, according to the examples described above with respect to FIGS.2, 3, 4, 5, and 6 . The embodiments described below are described in thecontext of LTE as the RAT. However, these embodiments may be applicableto any RAT.

In an example embodiment of a method for facilitating redirection to adedicated CN, a periodic timer with a shorter set time may be used. Aperiodic timer is a timer that is started at a WTRU when a signalingconnection, for example the NAS signaling connection, is released withthe serving CN node, for example the MME. In LTE, for example, theperiodic TAU timer is a general packet radio service (GPRS) timerdefined to have a range of values from 2 seconds to 3 hours and 6minutes. For example, when an MME determines from available informationthat the WTRU should be redirected toward a dedicated CN node, or whenthe MME allocates a special GUTI or GUMMEI, the MME may allocate a shortperiodic timer period. For instance, the MME may allocate a timer periodthat is shorter than the default value, which is 54 minutes for the TAUtimer in LTE. This may allow a WTRU to be more quickly redirected to thededicated CN node since the WTRU may perform the periodic TAU in ashorter time period than it would have had the default value been used.

AN MME is described in the previous embodiment; however, the embodimentmay be applicable for a UMTS/GERAN case where a serving GPRS supportnode (SGSN) may be the serving node for the PS domain, and the periodictimer may be referred to as a periodic RAU timer. An MSC/VLR may be theNAS entity in the CS domain where the corresponding timer is called theperiodic location area update (LAU) timer.

In another embodiment, the network may inform the WTRU whether it is adedicated network or not. The network may send an indication usingbroadcast or dedicated signaling. Broadcast signaling may make use ofRRC messages, for example system information blocks (SIBs), whereasdedicated signaling may be achieved using either RRC and/or NASmessages. For example, a new information element (IE) may be included inany NAS message to indicate if the CN node is a dedicated CN node ornot. This IE may be included in the Attach Accept message, the TAUAccept message, or any NAS session management message. Based on thisindication, the WTRU may decide to perform a re-registration (eitherwith an Attach or TAU Accept message) so that the RAN may choose adifferent/dedicated CN node.

The WTRU may also provide a dedicated CN indication to the eNB so thatthe eNB knows to forward the NAS message to an appropriate, dedicated CNnode. The WTRU may provide such an indication in an RRC message, such asan RRC connection request message or an RRC connection setup completemessage. The WTRU may be configured to use a dedicated CN node or may beconfigured to provide an indication about it being subject to the use ofa dedicated CN node, using an access network discovery and selectionfunction (ANDSF), an Open Mobile Alliance device management (OMA DM)procedure, a short messaging service (SMS), or any other configurationmethod, or it may be preconfigured in the universal integrated circuitcard (UICC)/mobile equipment (ME).

If the eNB receives an indication that a WTRU is subject to being servedby a dedicated CN node, the eNB may select a dedicated CN node to whichthe NAS message is forwarded. The eNB may also receive an identity(which may be included by the WTRU in the same manner described above),which the eNB may use to resolve the specific CN node to which theWTRU's NAS message is sent. Alternatively, the eNB may be configuredwith addresses of dedicated CN nodes, and the eNB may choose a dedicatednode using this configuration. Alternatively, the choice of a CN nodemay be a function of or dependent on an indication or identity providedby the WTRU as described above.

Additionally or alternatively, the WTRU may use a new establishmentcause to indicate that it is subject to the selection of a dedicated CNnode if the WTRU is configured to use a dedicated CN node. The NAS layermessages may include this information and may provide an establishmentcause to the RRC layer. Optionally, a new call type may be defined, suchas dedicated CN signaling or dedicated CN data, to indicate to the RRCthat the WTRU should use a dedicated CN node. The RRC may then set orinclude certain RRC parameters accordingly. Examples of parameters mayinclude an establishment cause and/or other indications as describedabove. Also, the WTRU may use a special random number in the RRCconnection request message instead of the S-TMSI when the networkbroadcasts that it is a dedicated node. This special random number may,for example, be recognized by the eNB by means of a pre-defined sequenceof bits. For example, the most significant bits of the random numberhaving said pre-defined sequence. Having received an RRC connectionrequest with said special random number, the eNB may then be able toeither route the initial NAS message to a dedicated node or notify thefirst MME that the WTRU is subject to dedicated CN node selection.

In addition, when a WTRU indicates to the eNB that it is configured touse a dedicated CN node, the eNB may pass that information to the firstMME. This way, if the MME already is a dedicated CN node, the MME maycontinue with the attach procedure and, if not, it may then request orcommand the eNB to reroute the attach message to another MME.

If the WTRU has asked for a combined attach, the MME may establish theSGW's association with the VLR. This way, the WTRU, following one of theprevious solutions, may perform a TAU later, and that TAU may be acombined one, which may cause the new relay MME to contact the VLR andalso establish the SGW's association.

Alternatively, the first MME may not contact the VLR and, instead, mayinform the WTRU in the Attach Accept message that a new CS registrationis recommended or needed. The Attach Accept message may include, forexample, a new IE or a new cause. This may be particularly useful wheresharing is deployed in the CN and the sharing operators have agreed touse designated entities for the dedicated CN nodes.

A re-route option was described above where a CN node, such as an MME,informs the eNB to route an NAS message to another CN entity that is aknown dedicated CN node or is expected to be a dedicated CN node. In anembodiment, the new MME may obtain the WTRU's NAS message, such as theAttach Request, the authentication context, vectors, or any generalsecurity context. Therefore, the re-route message may include thisinformation. The security context may be included in the re-route. Byway of example, the security context may be included in addition to theAttach Message and CN type.

There may be at least two ways to achieve including general securityinformation in the re-route message. The MME may send one container thatincludes both the WTRU message and the security parameters. Securityparameters may include, for example, authentication vectors and/or othersecurity contexts, parameters, or algorithms. Alternatively, an IE maybe included for each part. For example, one IE may be included for theWTRU message, one IE may be included for the authentication parameters,and one IE may be included for the security parameters, etc.

In an embodiment, the dedicated CN node may run the NAS security modecommand (SMC) procedure. The first MME may run the identityrequest/response and authentication request/response procedures, and thededicated CN node may run the SMC procedure. The operator may have thechoice to run no, one, or more than one procedure before re-routing themessage to a dedicated CN node. For example, the first MME may beconfigured to run no identification, authentication, or SMC procedures.The MME may then route the Attach Message. A lack of IEs related to, ordefined specifically for, WTRU identity, authentication context, andother security context, such as algorithms for ciphering and/orintegrity protection, may cause the dedicated CN node to runcorresponding identification, authentication, and SMC procedures.Alternatively, the first MME may only run the identificationrequest/response procedure and include information related to the WTRU'sidentity, such as the IMSI, in the re-route message. The lack ofauthentication and security parameters may inform the dedicated CN nodeto run procedures for these parameters. The first MME may either notinclude the related information or may include the corresponding IE butset the values to a well-known value, for example NULL or zero. A knownvalue may indicate to the dedicated CN node that it should run theseprocedures with the WTRU.

Alternatively, the first MME may explicitly indicate which procedures ithas run and which procedures need to be run by the dedicated MME.Alternatively, the first MME may indicate which procedures it has run,and the dedicated MME may implicitly know which other procedures mayneed to be run. To do so, the first MME may use a bitmap where each bitposition corresponds to a procedure, and the setting of the bit, whichmay be either “1” or “0,” may imply that the procedure has been run.Other explicit or implicit indications may be used, such as including anIE per procedure.

As disclosed above with respect to previously described embodiments, anMME may communicate with an HSS to receive subscription information. Inone example, the HSS may push subscription information to the MME when achange in the subscription information occurs.

A WTRU's subscription information may change at a CN, for example, whenthe CN has updated the WTRU profile information that indicates that theWTRU should be served by a dedicated CN node. When the WTRU'ssubscription information changes, the MME or SGSN may page the WTRU. TheMME or SGSN may use the IMSI as the WTRU's paging identity. Paging theWTRU by IMSI in the PS domain may force the WTRU to re-attach to thesystem. Hence, when paged with IMSI, the WTRU may re-attach to thesystem and the MME or SGSN may use any redirection solution for attachin order to redirect the WTRU to a dedicated CN node. Thus, the changeof WTRU profile information at the CN may trigger the CN to page theWTRU.

The change of WTRU profile information may also trigger the CN to pagethe WTRU with other identities, such as a S-TMSI in LTE and P-TMSI inUMTS. When the WTRU enters connected mode, for the case wherein the CNnode is an MME, the GUTI reallocation command may be used to reallocatea WTRU identity. For the case wherein the CN node is an SGSN, the P-TMSIreallocation command may be used to reallocate a WTRU identity. For thecase wherein the CN node is an MSC/VLR, the TMSI reallocation commandmay be used to reallocate a WTRU identity.

As referenced above, the network may page the WTRU with S-TMSI. Uponcompletion of the Service Request procedure, the network may initiate adetach procedure, for instance by sending a Detach Request to the WTRU,and may indicate “re-attach required”. This may cause the WTRU tore-attach to the system.

FIG. 7 depicts a signaling diagram of a method of redirecting a WTRU toa dedicated CN node when a Service Request procedure is performed. At701, the network, which may be an MME 720 for example, may page the WTRU710 to bring the WTRU 710 into connected mode. The MME 720 may also bean SGSN or MSC. At 702, the WTRU 710 may perform a Service Requestprocedure. The WTRU 710 may initiate a NAS connection establishment bysending a Service Request to the network. The network may be, forexample, an MME 720. At 703, the MME 720 may trigger a GUTI reallocationprocedure and respond to the WTRU 710 with a non-broadcast TAI orrouting area identity (RAI). The GUTI reallocation procedure mayadditionally or alternatively include the GUTI that points to adedicated core network. At 704, the MME 720 may then release RANresources associated with the WTRU 710. The WTRU 710 may then move to anidle mode. Thus, the next time the WTRU 710 enters connected mode, at705, the WTRU 710 may include the GUTI or at least part of the GUTI,such as the S-TMSI, in the TAU Request and may be redirected to adedicated MME. The WTRU 710 receiving the TAI or RAI may trigger theWTRU 710 to perform a TAU/RAU procedure and send a TAU/RAU request.Although not shown in FIG. 7 , the WTRU may communicate through an eNBto the MME. The MME or the eNB may redirect the WTRU to the dedicatedMME through a NAS redirection procedure.

Additionally or alternatively, the Service Request procedure may beresponded to by sending a GUTI reallocation command upon which the WTRU710 may consider the procedure to have completed and stop the timer thatguards the Service Request procedure. Alternatively, the GUTIreallocation procedure may be initiated after the CN node triggeredhandover command.

The MME 720 may also run the GUTI reallocation procedure if the firstmessage received from a WTRU 710 is the Detach Request message. This mayalso enable the system to redirect the WTRU 710 to a dedicated CN nodethe next time the WTRU 710 attaches to the system. Thus, for any NASprocedure that is not an attach or TAU procedure, if the MME is awarethat the WTRU 710 is subject to redirection to a dedicated CN node, theMME 720 may run the GUTI reallocation procedure to allocate an identitythat points to a specific CN node.

Although the example method depicted in FIG. 7 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

The examples described above may apply to LTE, GERAN and UMTS systemswhere the corresponding identity reallocation procedures may be usedaccording to the system/domain. For example, if a WTRU has a NASsignaling connection with the MSC in a GERAN or UMTS system, the MSC mayrun a TMSI reallocation command procedure as described above. For SGSN,a P-TMSI reallocation command procedure may be run as described above.

In order to speed up the redirection procedure, the CN may release theWTRU's connection with a cause code to force the WTRU to re-establish anew NAS connection. A new cause code may be defined at the RRC layer toindicate that the WTRU should re-attach to the system. Alternatively, anew cause code may be defined for the WTRU to perform a TAU procedure.

The examples described above may apply to GERAN and UTRAN systems wheresimilar procedures may be used, such as LAU for the CS domain and RAUfor the PS domain. Furthermore, the eNB may be replaced by a BSC and anRNC for GERAN and UMTS systems, respectively.

Alternatively, an existing mechanism may be used to quickly redirect theWTRUs. The MME may use a load balancing procedure, which may cause theS1 and RRC connections to be released. The RRC may include a releasecode set to “load balancing TAU required,” which may force the WTRU toperform a TAU. Thus, with the GUTI being re-allocated such that it canpoint to a specific MME, using the load balancing procedure may enable aquick redirection.

Thus, with any NAS procedure, such as a TAU or Service Request, a GUTIreallocation may be used to first provide the WTRU with an identity thatpoints to a specific CN, and then the WTRU's connection may be releasedas described above in order to make the redirection faster.

Another alternative is that, for a given NAS procedure or connected mode(CM) Service Request (MSC), the CN node may first run the correspondingidentity procedure. After its completion, the CN node may reject the NASprocedure with Service Reject or CM Service Reject, and the CN node mayindicate that the WTRU is implicitly detached. For example, a cause codefor the PS domain of UMTS and LTE may be used. Other causes that maylead the WTRU to re-establish a NAS signaling connection, such as tore-register, may also be used if applicable. Alternatively, a new causecode may be defined that may force the WTRU to re-register to thesystem. For example, the WTRU may perform an attach or an updateprocedure, such as a TAU, RAU, or LAU.

In an embodiment, the CN node may reallocate the identity after theService Request procedure completes. For example, the MME may send aGUTI reallocation command message, the SGSN may send a P-TMSIreallocation command message, or the MSC/VLR may send the TMSIreallocation command message.

In an example embodiment wherein the CN node is an MME, the MME mayreceive a Service Request message or an Extended Service Request messageand the profile information of the WTRU, as provided by the HSS. Theprofile information may indicate that the WTRU should be served by adedicated CN node. The MME may initiate a GUTI reallocation commandprocedure/message before or after the completion of the Service Requestprocedure. If the GUTI reallocation command is run before the completionof the Service Request procedure, the MME may optionally send a ServiceReject with a cause code that may force the WTRU to re-attach to thesystem.

In an example embodiment wherein the CN node is an SGSN, the SGSN mayreceive a Service Request message and the profile information of theWTRU, as provided by the HSS/HLR. The profile information may indicatethat the WTRU should be served by a dedicated CN node. The SGSN mayinitiate a P-TMSI reallocation command procedure/message before or afterthe completion of the Service Request procedure.

In an example embodiment wherein the CN node is an MSC/VLR, the MSC/VLRmay receive a CM Service Request message and the profile information ofthe WTRU, as provided by the HSS/HLR. The profile information mayindicate that the WTRU should be served by a dedicated CN node. TheMSC/VLR may initiate the TMSI reallocation command procedure/messagebefore or after the completion of the Service Request procedure.

Redirection with GUTI re-allocation may be used for any initial NASmessage that a WTRU sends, for example a paging response in GERAN, andmay not limited to the Service Request or CM Service Request messages.For any NAS procedure or message that the WTRU sends, the CN may decideto reallocate the identity, for example via a GUTI reallocation command,before or after the procedure completes. The CN may decide, for example,based on a change of subscription information such that it indicates theuse of dedicated CN node for the WTRU.

Furthermore, the CN node, which may be for example an MME, SGSN, orMSC/VLR, may run the identity reallocation procedure at any time whenthe WTRU is in connected mode. Identity reallocation procedures mayinclude, for example, a GUTI reallocation command for a MME, a P-TMSIreallocation command for an SGSN, or a TMSI reallocation command for anMSC/VLR. In an example embodiment, a WTRU may be involved in an ongoingdata transfer and if the subscription or profile information of the WTRUis updated such that the WTRU should be served by a dedicated CN node,the appropriate WTRU identity reallocation procedure may be executed.

Additional embodiments are disclosed herein addressing how to handlerace conditions during redirection with a CN triggered handover. In anembodiment, a CN-triggered handover may force the eNB to select a newMME without affecting the WTRU. The CN may trigger the handover at anytime after the attach procedure is completed. If handover is triggeredby the CN, it may be possible for the WTRU or the eNB to start adifferent procedure. For example, the WTRU may begin a sessionmanagement procedure to initiate the activation of a PDN connection or anew dedicated bearer. Additionally or alternatively, the MME may startthe MME-initiated handover. In another example embodiment, the eNB maybe in the process of handing over the WTRU to another eNB either usingS1 or X2 handover, and, at the same time, the MME may initiate thehandover toward the eNB for redirecting the WTRU.

Although the CN-initiated handover scenario may be used to exemplify themethods to handle race conditions, these methods may be applied tosimilar race conditions in other solutions.

In another embodiment, a race condition may be handled for aCN-initiated handover during an ongoing RAN handover. Upon reception ofa CN-initiated handover request to redirect the WTRU, if the RAN node,for example an eNB, RNC, or BSC, is executing a handover, the RAN nodemay reject the request and indicate that the reason is ongoing handover.Upon reception of a rejected request for CN-initiated handover, whichmay be received from a RAN node, the CN node may wait until the handoveris complete before initiating a new request. The CN may determine thatthe handover is complete when the CN receives confirmation of thehandover completion from the target RAN node. For example, in LTE, theCN may determine a handover is complete when it receives a path switchrequest message from the target eNB.

In yet another embodiment, the handling of other procedures during anongoing CN-initiated handover is addressed. During a CN-initiatedhandover, the CN may receive a request from either the WTRU or theSGW/PGW to activate, deactivate, or modify a bearer. The handling ofthis request may depend on whether the handover succeeds or fails.

The MME may take the following actions when it receives a request toactivate, deactivate, or modify a bearer from the SGW/PGW and the MMEhas initiated a handover to redirect the WTRU. The MME may reject therequest and include a cause code to indicate that there is a handover inprogress. For example, if the MME receives a Create Bearer Request fromthe SGW, the MME may respond with a Create Bearer Response and include acause value to indicate that the handover is in progress. The MME mayinclude a timer after which the destination node, such as an SGW or PGW,may retry. Upon reception of a response indicating that handover is inprogress, the SGW or PGW may retry the request after a certainpre-configured time or after the indicated time elapses. Upon receptionof this response, the SGW may either retry after a time elapses asdescribed above, or it may in turn send a Create Bearer Response to thePGW and include the same cause code and timer value, if present. The PGWmay later retry the request. Alternatively, an existing cause code maybe used. For example, WTRU may refuse or is unable to page the WTRU.

The MME may take the following actions when it receives a request toactive, deactivate, or modify a bearer from a WTRU and the MME hasinitiated a handover to redirect the WTRU. The MME may ignore therequest, which may eventually cause a timer to expire at the WTRU. TheWTRU may request again later. The MME may reject the request and includean existing or new cause code that may either inform the WTRU that ahandover is pending or that the WTRU should retry. The MME may rejectthe request and include an NAS session management back-off timer with avalue set to zero or any other non-zero but short value. The MME mayinitiate a routing procedure of this request if the MME receives aconfirmation that the handover has been successful. The MME may forwardthe request to a new MME when the new MME requests the WTRU's context. Anew IE or procedure may be defined. The new IE may be included in thecontext response that the source MME sends to the target dedicated MME.This new IE may hold the WTRU's NAS message. Upon reception by thetarget MME, the target MME may process the request and respond to itaccordingly.

Alternatively, if the eNB determines that there is an ongoing handoverto redirect the WTRU, the eNB may not forward the request to the sourceMME. The eNB may later forward the NAS message to the target MME afterthe handover is complete. Alternatively, the eNB may not acknowledge thereceipt of the message over RRC, PDCP, RLC, MAC, etc., which may thenforce the WTRU to re-send the NAS message. By then, if the handover iscomplete, the eNB may forward it to the new MME.

In an embodiment, a CN node, such as an, MME, SGSN, or MSC, may performa re-allocation of the WTRU identity after the handover is complete toprovide the WTRU with a new ID that points to the actual serving CNnode. This serving CN node may be the CN node that has the WTRU contextafter the handover. After the CN-triggered handover, the targetdedicated MME may now have the WTRU context and may initiate a GUTIre-allocation command toward the WTRU and assign a new GUTI. Similarly,a target or new SGSN may run a P-TMSI reallocation procedure after thehandover is complete in order to provide the WTRU with a new identitythat may point to the serving SGSN. Similarly, a target or new MSC/VLRmay run a TMSI reallocation procedure after the handover is complete inorder to provide the WTRU with a new identity that points to the servingMSC/VLR.

During the identity re-allocation procedure described above, the CN mayinclude a non-broadcast identity in the procedure. Example identityreallocation procedures include a GUTI reallocation command for LTE, aP-TMSI reallocation command for the PS domain of a GPRS/UMTS system, ora TMSI reallocation command for the CS domain of GPRS/UMTS system. In anLTE example, during the GUTI reallocation command described above, theMME may also include a non-broadcast TAI in the message, such as a GUTIreallocation command, that is sent to the WTRU. This may help speed up aregistration from the WTRU. When the WTRU reads the system information,it may realize that the allowed TAI list as provided by the MME in theGUTI reallocation command is not equivalent to what is actually beingbroadcast by the RAN. Hence the WTRU may immediately send a registrationmessage, such as a TAU, to the MME.

A similar example may apply to an SGSN and an MSC/VLR with correspondingmessages. For example, during a P-TMSI reallocation command, an SGSN mayalso include a non-broadcast RAI for the WTRU. Similarly, when the WTRUrealizes that a broadcast RAI is not equivalent to the non-broadcast RAIas provided in the P-TMSI reallocation command, the WTRU may then sendan RAU to the SGSN. Similarly, during a TMSI reallocation command, theMSC/VLR may also include a non-broadcast location area identity (LAI)for the WTRU. When the WTRU realizes that a broadcast LAI is notequivalent to the non-broadcast LAI as provided in the TMSI reallocationcommand, the WTRU may then send an LAU to the MSC/VLR.

Additional example embodiments provide solutions for switching from adedicated CN to a non-dedicated CN. When a WTRU is alreadyattached/registered to a dedicated CN node, the WTRU may find it needsto switch back to the non-dedicated CN node. The following events maytrigger a switch back to a non-dedicated CN node. The WTRU may receivean indication from the dedicated CN node that it is overloaded. In sucha scenario, the WTRU may receive an Attach Reject, a TAU Reject, or aService Reject with a mobility management back-off timer from thededicated CN node. Upper layer data transmission errors may indicatethat the dedicated CN node, such as a dedicated SGW or PGW, ismalfunctioning. A WTRU may be scheduled to remain attached to thededicated CN node for some portion of a day and then attach to thenon-dedicated CN node for the rest of the day. The Access Point Name(APN) that the WTRU requested to access may not be supported by thededicated CN node.

FIG. 8 is a diagram of an example method of a WTRU switching from adedicated CN node to a non-dedicated CN node. In the example illustratedin FIG. 8 , at 801 a WTRU 810 may be attached to a dedicated CN. At 802,a condition being satisfied may trigger the WTRU 810 to switch from thededicated network to the non-dedicated one. At 803, the WTRU 810 maydetach from the dedicated CN node by sending a Detach Request and theninitiate a new Attach Request at 804. A new detach type may be defined.A new indication may be included in the new Attach Request to inform thenon-dedicated MME 830 that it should ignore the subscription data thatindicates that the WTRU 810 should be redirected to a dedicated CN node.The Attach Request may further include an indication of a length of timeduring which the non-dedicated MME 830 should ignore the subscriptiondata. Upon receiving this indication, the non-dedicated MME 830 maytreat the Attach Request as a normal WTRU Attach Request and will notredirect the Attach Request, and hence the WTRU 810, to the dedicated CNnode.

In order for an eNB to route the new Attach Request to the non-dedicatedMME 830, the WTRU 810 may omit the S-TMSI, which has the MME code of thededicated MME 820, from the RRC Connection Request message. The methodsdescribed above for including some indication in the RRC message toforce the eNB to choose the dedicated CN node may also be used similarlyto force the eNB to choose the normal MME for this new Attach Request.

Additionally or alternatively, the WTRU 810 may indicate to thenon-dedicated MME 830 how long the WTRU 810 should be attached to thenon-dedicated CN. After that period of time, the non-dedicated MME 810may redirect the WTRU 810 to the dedicated MME 820 again. Alternatively,the length of time that the WTRU 810 may be attached to thenon-dedicated MME 830 may be pre-configured in the MME or may beincluded in the WTRU's subscription data.

Although the example method depicted in FIG. 8 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 9 is a diagram of an example method of a dedicated CN nodeinitiating a procedure to switch back a WTRU to the non-dedicated CNnode. At 901, a WTRU 910 may be attached to the dedicated MME 920. Thededicated MME 920 may decide to detach the WTRU 910 for any number ofreasons. By way of example, at 902, the dedicated MME 920 may becomeoverloaded and decide that the WTRU 910 should be detached. At 903, thededicated MME 920 may explicitly send a Detach Request to the WTRU 910with some indication that the WTRU 910 should re-attach to thenon-dedicated MME 930. For example, a new detach type may be defined toserve as this indication. After the Detach Request, at 904, the WTRU 910may send an Attach Request to the non-dedicated MME 930. As describedabove, the Attach Request may include a new indication to inform thenon-dedicated MME 930 that it should ignore the subscription data thatindicates that the WTRU 910 should be redirected to a dedicated CN nodeand may further include an indication of a length of time during whichthe non-dedicated MME 930 should ignore the subscription data.Alternatively, although not depicted in FIG. 9 , after receiving aDetach Request from the dedicated MME 920, the WTRU 910 may explicitlysend a Detach Request to detach from the dedicated MME 920 and thenre-attach to the non-dedicated MME 930.

Although not depicted in FIG. 9 , the dedicated CN node may include anindication in a TAU Reject or Service Reject message to request the WTRU910 to re-attach to the non-dedicated CN node.

Although the example method depicted in FIG. 9 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

As described above, a target MME may receive a NAS message, such as aService Request, from a WTRU for which the MME does not contain acontext. In order to avoid this, the eNB may include the GUMMEI andS-TMSI in an initial WTRU message procedure that is sent on the S1APinterface. Therefore, when the eNB receives a GUMMEI from the WTRU aspart of the RRC connection procedure, such as in theRRCConnectionSetupComplete message, the eNB may verify if the GUMMEIcontains a null-MMEGI.

If the GUMMEI contains a null-MMEGI, the eNB may include the GUMMEI inthe initial WTRU message sent to the target MME. In this case, theinitial WTRU message is sent to the dedicated MME since the eNB sendsthe NAS message to the dedicated MME based on the GUMMEI. The dedicatedMME may receive the initial NAS message for a WTRU in question via theeNB.

The target MME may know if it is configured to operate as a dedicatedMME. The target MME may verify if the MMEGI in the GUMMEI has a value ofa null-MMEGI. If a null-MMEGI is included in the GUMMEI, the target MMEmay process the NAS message and not reject it even if the MME does notcontain a context for this WTRU.

The target MME may fetch the WTRU context from the source MME using theinformation received from the eNB, such as by using the GUMMEI andS-TMSI. For example, if the initial NAS message is an Extended ServiceRequest or Service Request (collectively referred to as ServiceRequest), the target MME, even if it does not contain a context for theWTRU, may fetch the WTRU context from the source MME based on the checkdescribed above.

While the target MME fetches the context, the source MME may provide thetarget MME with any subscription information that indicates if the WTRUshould be served by a dedicated CN. The source MME may provide thetarget MME with an indication of whether the WTRU should be served by adedicated MME only, a dedicated MME and SGW, or a dedicated MME, SGW andPGW. For example, if the subscription information or context informationindicates that the PGW should be re-allocated to be a dedicated PGW, thetarget MME may then determine to trigger the WTRU to re-attach.

Alternatively, after the target MME gets the WTRU context, the targetMME may verify using domain name system (DNS) or other methods if itneeds to re-allocate the WTRU's PGW and force the WTRU to re-attach.

After the context is fetched, the target MME may respond to the WTRUusing any of the methods described herein.

An MME may, even if it has fetched the WTRU context, respond with aService Reject, but include a cause code that triggers the WTRU tore-attach to the system, optionally using a cause code that does notlead the WTRU to delete the GUTI.

For example, an MME may send a Service Reject and include a cause code“#10—Implicitly detached”. Alternatively, the MME may use cause code“#40—No EPS bearer context activated”. The Service Reject may be usedwith the cause codes as described above if the MME needs to re-allocatea dedicated PGW. If the NAS message is a TAU Request, the MME may stillreject the TAU and include a cause code that forces the WTRU tore-attach to the system, optionally with a cause code that does notcause the GUTI to be deleted at the WTRU, for example cause code #10 or#40.

In another embodiment of a method for forcing the WTRU to re-attach tothe system, an MME may initiate a bearer context deactivation andidentify the bearer to be the default bearer. For any reason or at anytime that the MME wants the WTRU to re-attach to the system, such as forthe purpose of using dedicated CN nodes, the MME may send the DeactivateEPS Bearer Context Request and include a cause code that may trigger theWTRU to eventually re-attach to the system. The re-attachment may occurafter the performance of an explicit detach.

For example, the MME may use cause code “#39—reactivation requested”.This may trigger a WTRU redirection to a dedicated CN regardless of theactual redirection solution. Redirection solutions may include are-route of attach solution, or null-MMEGI solutions, etc. The MME maydeactivate a default bearer and the overall PDN connection of the WTRUat any time, with or without GUTI reallocation.

Alternatively or additionally, an MME may initiate the detach procedureif the MME requires that the WTRU re-attach to the system for thepurpose of redirecting the WTRU to a dedicated CN node. At any time, theMME may decide to redirect the WTRU and may require that the WTRUre-attach, for example in order to reselect another dedicated PGW. TheMME may send the Detach Request message to the WTRU and include thedetach type IE with a value set to “re-attach required”. This method maybe deployed in conjunction with other methods described herein. Forexample, the MME may first perform GUTI reallocation, then initiate thedetach procedure by sending a Detach Request and indicating “re-attachrequired” as the detach type.

If the MME can continue serving the WTRU without PGW re-allocation, theMME may use the fetched WTRU context and accept the WTRU's request.However, if the MME needs to re-allocate the SGW, the MME may inaddition trigger an SGW re-allocation to pick an SGW that is a dedicatedSGW. The MME may perform an SGW re-allocation as part of the ServiceRequest procedure or alternatively after the Service Request procedureis complete.

As described above, a source MME, which may be a non-dedicated MME, or atarget MME, which may be a dedicated MME, may trigger a WTRU re-attach.Methods for triggering WTRU re-attach by a non-dedicated and dedicatedMME will now be described.

For WTRUs that are already registered in the system, the reselection ofa PGW may require re-attaching the WTRU if a dedicated PGW is desired.

Configurations in the source MME may indicate if the re-attach should betriggered by the source MME before redirection. When the source MMEreceives updated subscription information to redirect the WTRU, or dueto any local policy that requires the redirection of a WTRU to adedicated CN, the source MME may first verify if the PGW needs to bere-selected. This may be done using DNS or other local policies or otherfunctionalities. If the PGW also needs to be redirected, the MME mayverify its local policies to see if it should re-attach the WTRU orredirect the WTRU and leave it up to the target MME to perform there-attach.

If MME policies or configurations indicate that the MME should performWTRU re-attach, the MME may employ any of the methods described above toredirect the WTRU. For example, the MME may initiate a WTRU DetachRequest procedure and include the type set to “re-attach required,” orthe MME may deactivate the PDN connections of the WTRU. Whiledeactivating the last PDN connection or the last default bearer, thenetwork may indicate “#39—reactivation requested” in the NAS sessionmanagement message as explained above.

After re-attaching the WTRU as described above, the source MME mayredirect the WTRU to a dedicated target MME. The source MME may forwardinformation to the target MME, for example, when the target MME attemptsto fetch the WTRU context from the source MME. The information mayindicate that a redirection of MME and/or SGW only is needed in order toavoid reselection of a PGW which may trigger another re-attach at thetarget MME.

The source MME may have configurations to let the target MME re-attachthe WTRU if necessary. As such, when the subscription changes such thatthe WTRU should be redirected to a dedicated MME, the source MME mayperform the redirection and defer to the target MME to evaluate if are-attach is still needed for the WTRU. After redirecting the WTRU, thetarget MME may fetch the WTRU context from the source MME. The sourceMME may include the relevant subscription information in the WTRUcontext to inform the target MME if the PGW should also be redirected.Alternatively, upon reception of the subscription information from thesource MME or from the HSS, the target MME may further determine if thePGW needs to be re-allocated. The target MME may make the determination,for example, using DNS or other methods.

If the PGW needs to be re-allocated, the target MME may initiate a WTRUre-attach using any of the methods described above. For example, thetarget MME may reject the WTRU's NAS message and indicate that are-attach is required.

It is important to note that all of the methods and procedures describedabove also apply to other RATs such as GERAN and UTRAN systems with thecorresponding procedures at the NAS or RAN-to-Core Networkinterfaces/protocols. Thus, even though the methods are described in thecontext of LTE, they apply to other systems accordingly.

FIGS. 10A and 10B are a signal flow diagram of an example method forperforming WTRU redirection. With respect to FIG. 10A, at 1001, a WTRU1010 is registered with a serving non-dedicated MME 1030. At 1002, theHSS 1060 may update the user profile 1002 in the MME 1030 to indicatethat the WTRU 1010 should be served by a dedicated MME 1040. The HSS1060 may do so by pushing subscription information to the MME 1030. At1003, the serving MME 1030 may verify if the PGW needs to be reselectedor redirected to be a dedicated PGW. At 1004 a and 1000 b, the MME 1030may optionally proactively redirect the WTRU 1010 by paging the WTRU1010 if the WTRU 1010 is in idle mode. At 1004 a, an S1AP paging messagemay be sent by the Serving MME 1030 to the eNB 1020 and at 1004 b an RRCpaging message may be sent by the eNB 1020 to the WTRU 1010.Alternatively, at 1005 the MME 1030 may wait until the WTRU 1010performs a Service Request or Extended Service Request. If the MME 1030waits until the WTRU 1010 performs a Service Request, paging may notoccur.

If the WTRU is already in connected mode, step 1006 as illustrated inFIG. 10A may occur directly after 1003. At 1006, the Serving MME 1030may reallocate a GUTI to the WTRU 1010 based on the updated subscriptioninformation. This may be accomplished at 1006 a by the MME 1030 sendinga GUTI Reallocation Command containing null-MMEGI and a non-broadcastTAI to the WTRU 1010. At 1006 b, the WTRU 1010 may respond to the MME1030 with a GUTI Reallocation Complete message. Again, as noted above,similar procedures may be used in GERAN and UTRAN between the WTRU andthe SGSN using the corresponding NAS messages. For example, a P-TMSIReallocation Command may be used instead of the GUTI RealloationCommand.

With respect to FIG. 10B, at 1007, the MME 1030 may trigger the WTRU1010 to reattach by sending a Detach Request with a type set to“reattach required” at 1007 a. At 1007 b, the WTRU 1010 may then respondwith a Detach Accept 1007 b. At 1008, at the next WTRU TAU, which may besent by the WTRU 1010 after transitioning to idle mode, the eNB 1020 mayselect a dedicated MME 1040. This may be accomplished at 1008 a by theWTRU 1010 sending an Attach Request including a GUMMEI indicatingnull-MMEGI in an RRC message and at 1008 b the eNB 1020 forwarding theAttach Request to the dedicated MME 1040 based on the null-MMEGI.

Although the example method depicted in FIG. 10 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

FIG. 11 is a diagram of an example location update procedure initiatedby a non-dedicated MME 1130. At 1101, the non-dedicated MME 1130 maysend a Handover Trigger message to the eNB 1120. At 1102, the eNB 1120may respond with a Handover Required message. At 1103, the non-dedicatedMME 1130 may send a Forward Reallocation Request message to thededicated MME 1140. The Forward Reallocation Request message may includethe registered LAI, VLR number, and/or a CSFB flag to indicate that theWTRU 1110 was registered with a MSC/VLR 1150 and there are active SGWassociations between the non-dedicated MME 1130 and the MSC/VLR 1150.Upon receiving the Forward Reallocation Request and the aforementionedflag or registered LAI or VLR number in the message, if the dedicatedMME 1140 supports CSFB function, the dedicated MME 1140 may initiate aLocation Update procedure toward the registered MSC/VLR 1150 on behalfof the WTRU. At 1104, the dedicated MME 1140 may send a Location UpdateRequest to the MSC/VLR and at 1105 receive a Location Update Accept inresponse. At 1006, the eNB 1120 and dedicated MME 1140 may then exchangeHandover Request Acknowledge messages. At 1107, the dedicated MME 1140may then send a Forward Relocation Response to the non-dedicated MME1130. At 1108, the non-dedicated MME 1130 may then send a HandoverCommand to the eNB 1120.

Although the example method depicted in FIG. 11 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

Alternatively, the dedicated MME may send a Detach Request to the WTRUwith type set to “IMSI detach” in order to trigger the WTRU to perform are-attach for non-EPS services. The dedicated MME may send the DetachRequest based on the information received from the non-dedicated MMEabout the WTRU's combined registration. Such information may include theCSFB flag, registered LAI, VLR number/address, TMSI, etc. Thus, when aTAU is then performed with type set to “IMSI attach” or when the WTRUwants to register for CS services, the MME may send a Location UpdateRequest on the SGW's interface.

FIG. 12 is a diagram of an example IMSI detach procedure when thededicated MME 1240 does not support CSFB functionality. At 1201, thenon-dedicated MME 1230 may send a Handover Trigger message to the eNB1220. At 1202, the eNB 1220 may respond with a Handover Requiredmessage. At 1203, the non-dedicated MME 1230 may send a ForwardReallocation Request message to the dedicated MME 1240. The ForwardReallocation Request message may include the registered LAI, VLR number,and/or a CSFB flag to indicate that the WTRU 1210 was registered with aMSC/VLR 1250 and there are active SGW associations between thenon-dedicated MME 1230 and the MSC/VLR 1250. At 1204, the eNB 1220 anddedicated MME 1240 may then exchange Handover Request Acknowledgemessages. At 1205, if the dedicated MME 1240 doesn't support CSFBfunction, it may return an indication in the Forward Relocation Responsemessage that the CSFB is not supported. Upon receiving such anindication, at 1205 the non-dedicated MME 1230 may send a HandoverCommand to the eNB 1220. At 1206, the non-dedicated MME 1230 mayinitiate IMSI detach procedure toward the registered MSC/VLR 1250.

Although the example method depicted in FIG. 12 shows messages and/orsteps in a particular order, it should be recognized that not allmessages and/or steps may be necessary and the particular order may bedifferent. Furthermore, whereas steps and/or messages may be depicted asseparate events, the steps and/or messages may be combined as a singleevent. Likewise, a single event may be broken out into multiple events.

The methods and procedures discussed above apply to combined proceduresin GERAN and UTRAN, as well using the corresponding interfaces andprotocol messages. The methods and procedures described above may alsoapply with any existing redirection methods and procedures. For example,using any of the existing redirection methods, a target MME may fetchthe WTRU context from the source MME which should then provide theindications described above. The target MME may take the actionsdescribed above based on these indications.

The embodiments described above may also be used to move a WTRU from adedicated CN node to a non-dedicated CN node if the WTRU's subscriptioninformation changes or if the local policies at the serving CN requiresuch behavior.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A method performed by a base station, the methodcomprising: receiving, by the base station, a first indication from awireless transmit receive unit (WTRU) to direct a non-access stratum(NAS) message to a core network node associated with a specific service;transmitting, by the base station and to the WTRU, a message including asecond indication to associate with a different core network node; andtransmitting, by the base station and to the WTRU, data for the specificservice from the different core network node.
 2. The method of claim 1,wherein the first indication includes an identity associated with thecore network node.
 3. The method of claim 1, further comprisingtransmitting information indicating that the WTRU is subject to aconfiguration that uses the core network node.
 4. The method of claim 1,wherein the first indication is received during radio resource control(RRC) connection establishment.
 5. The method of claim 1, furthercomprising: selecting the different core network node based on the firstindication.
 6. The method of claim 1, wherein the WTRU is connected tothe different core network node.
 7. The method of claim 1, wherein thetransmitting the message including a second indication to associate withthe different core network node is based on a change in subscriptioninformation.
 8. The method of claim 1, wherein the transmitting themessage including a second indication to associate with the differentcore network node is based on a load of the core network node.
 9. Themethod of claim 1, further comprising transmitting an indication to theWTRU to perform mobility registration.
 10. The method of claim 9,further comprising releasing a connection to the WTRU to allow the WTRUto enter an idle mode to enable redirection to the different corenetwork node.
 11. A base station comprising: a receiver configured to:receive a first indication from a wireless transmit receive unit (WTRU)to direct a non-access stratum (NAS) message to a core network nodeassociated with a specific service; and a transmitter configured to:transmit, to the WTRU, a message including a second indication toassociate with a different core network node; and transmit, to the WTRU,data for the specific service from the different core network node. 12.The base station of claim 11, wherein the first indication includes anidentity associated with the core network node.
 13. The base station ofclaim 11, wherein the transmitter is further configured to transmitinformation indicating that the WTRU is subject to a configuration thatuses the core network node.
 14. The base station of claim 11, whereinthe first indication is received during radio resource control (RRC)connection establishment.
 15. The base station of claim 11, furthercomprising a processor configured to select the different core networknode based on the first indication.
 16. The base station of claim 11,wherein the WTRU is connected to the different core network node toreceive the data.
 17. The base station of claim 11, wherein the messageincluding a second indication to associate with the different corenetwork node is based on a change in subscription information.
 18. Thebase station of claim 11, wherein the message including a secondindication to associate with the different core network node is based ona load of the core network node.
 19. The base station of claim 11,wherein the transmitter is further configured to transmit an indicationto the WTRU to perform mobility registration.
 20. The base station ofclaim 19, wherein a connection to the WTRU is released to allow the WTRUto enter an idle mode to enable redirection to the different corenetwork node.